Upland phosphorus

Lehmann, J., Cravo, M.D., de Macedo, J.L.V., Mor-eira, A. and Schroth, G. (2001) Phosphorus management for perennial crops in central Amazonian upland soils. Plant and Soil 237, 309-319. 

Hedley, M.J., Kirk, G.J.D. and Santos, M.B. (1994) Phosphorus efficiency and the forms of soil phosphorus utilized by upland rice cultivars. Plant and Soil 158, 53-62. 

Livingstone, D., Khoja, T.M. and Whitton, B.A. (1983) Influence of phosphorus on physiology of a hairforming blue-green alga Calothrix parietina) from an upland stream. Phycologia 22, 345-350. 

Turner, B.L., Chudek, J.A., Whitton, B.A. and Baxter, R. (2003c) Phosphorus composition of upland soils polluted by long-term atmospheric nitrogen deposition. Biogeochemistry 65, 259-274. 

Dobermann, A., George, T. and Thevs, N. (2002) Phosphorus fertilizer effects on soil phosphorus pools in acid upland soils. Soil Science Society of America Journal 55, 552-560. 

During the last decade, information on the organic phosphorus composition of soil solutions and water extracts has been obtained by phosphatase hydrolysis. This technique not only gives structural information on filterable organic phosphorus, but also indicates its potential biological availability. In solution from Scottish upland soils, up to 64% of the filterable organic phosphorus was hydrolysed by non-specific phosphatases (Shand and Smith, 1997), while hydrolysable unreactive phosphorus in water extracts of Australian pasture soils was dominated by phosphate diesters and myo-inositol hexakisphosphate (Turner et al., 2002a). Only small concentrations of labile monoesters were detected in the latter study, possibly due to the rapid hydrolysis of labile compounds by soil phosphatase enzymes. 

Turner, B.L., Chudek, J.A., Whitton, B.A. and Baxter, R. (2003b) Phosphorus composition of upland soils polluted by long-term atmospheric nitrogen deposition. Biogeochemistry 65, 259-274. Turner, B.L., Driessen, J.P., Haygarth, P.M. and Mc-Kelvie, I.D. (2003c) Potential contribution of lysed bacterial cells to phosphorus solubilisation in rewetted Australian pasture soils. Soil Biology and Biochemistry 35, 187-1 89. 

Typically, phosphorus is added in various forms to a watershed (Figure 9.1). These include fertilizers, nonhazardous wastes (animal manures and biosolids), and nutrient-enriched waters. Historically, organic wastes such as animal manures were applied to agronomic crops and pastures on the basis of the nitrogen availability, which has resulted in excessive application of phosphorus. As a result, many uplands used for land application of wastes have accumulated phosphorus in excess amounts. A major portion of the phosphorus added to uplands is retained within the soil. However, as upland soils become saturated or overloaded with phosphorus, a significant portion of the stored phosphorus can be released and transported with water during runoff events. 

Numerous published articles evaluated the potential of wetlands to retain phosphorus. Most of this information is related to inflow and outflow characteristics of the water, with very limited information on internal processes and mass balances of phosphorus in wetlands. However, a wealth of quantitative information on phosphorus biogeochemistry of upland and of other aquatic ecosystems provides extensive process-level information. These data on chemical and biological reactions regulating phosphorus availability and mobility in soils and sediments form a basis for much of the phosphorus biogeochemistry research related to phosphorus retention in wetlands. For example, early research on flooded soils showed the regulation of phosphorus solubility and retention by oxidation and reduction of iron. Similarly, iron regulation of phosphorus solubility was also shown in lake sediments. More recent research in wetlands also confirmed that these principles are applicable to wetland ecosystems. 

Wetlands and aquatic systems are recipients of phosphorus loads from upland systems. Increased loading of phosphorus to a system can cause nitrogen limitations. The phosphorus enrichment of P-limited systems leads to eutrophication and ecosystem stress. The phosphorus cycle does not have a significant gaseous loss mechanism. Thus, most of the added P accumulates in the systems. 

HARRISON A.F. 1978. Phosphorus cycles of forest and upland grassland systems and some effects of land management practices. In Phosphorus in the Environment Its Chemistry and Biochemistry, CIBA Foundation Symposium, 57. Excerpta Medica. pp.I75-I95. 

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